Known centrifugal separation devices commonly use a drive motor for the scraper blade and a drive motor for the bowl, with both motors being indirectly coupled to the scraper blade and the bowl through belts and pulleys. Strobe devices are used to synchronize the drive motors and the rotational speed of the scraper and bowl. Other prior art centrifugal separators also commonly use a friction clutch to synchronize the rotational speeds of the blades and the bowl. Friction clutches, however, have a tendency to wear and slip and, therefore, do not provide consistent synchronous blade and bowl rotation, especially during drag-inducing conditions such as start up and the injection of the particle contaminated fluid into the bowl during operations.
The centrifuge separator of U.S. Pat. No. 6,149,573 provides a solution to the slippage issues surrounding synchronization of the speeds of the bowl and blade. A centrifugal clutch is engaged to link the blade with the bowl during centrifuge operations. The clutch is disengaged when blade operation is necessary to scrape the inside of the bowl. Separate drive motors are engaged with the blade and bowl respectively. The use of separate drive motors remains an undesirable, complicated and costly feature of the '573 patent.
The complications of the '573 are resolved, in part, by the structure shown in U.S. Pat. No. 6,478,724. In one embodiment of the '724 patent (FIGS. 3–6), a spindle is attached to the centrifuge bowl and a shaft, centered within the spindle for independent rotation, is engaged with the scraper mechanism. A shiftable clutch assembly operable to engage with two sets of interlocking teeth shifts the motive force between the spindle, shaft and a combination of both. In a first position, the clutch engages the spindle and shaft together so the bowl and scraper are driven to rotate synchronously. In a second position, the first and second sets of teeth are disengaged and the scraper is free to rotate on its own. Both spindle and shaft are engaged with a single driver motor in a belt and pulley combination. We believe the mechanical structure needed for the centrifuge of the '724 patent to still be unnecessarily complicated and costly. Further, undesirable slippage of the belt/pulley drive mechanism will occur under loaded operations.
A recent invention provides an apparatus for enhancing the operation of a centrifugal separator and automatically adjusting for varying amounts of solids in the contaminated fluid being passed through the separator. That invention includes a load sensing circuit which monitors the load on the drive motor of the separator centrifuge bowl and signals for a cleaning cycle based upon the load information. See U.S. Pat. No. 5,454,777, which is incorporated herein by reference.
The separator of the '777 patent requires a first drive motor for rotating the centrifuge bowl and a second drive motor for rotating the scraper blades. A load sensing device in combination with a programmable logic controller (PLC) co-operate to coordinate the operation of the separate motors.
It is therefore an object of this invention to provide a centrifugal separate having a single drive motor, yet being less complicated mechanically and less costly than those shown in the prior art.
It is a further object of this invention to provide a direct drive to the bowl and scraper mechanism to eliminate the potential for slippage such as that created by loading of the prior art gear/chain, belt pulley engagements from the drive motor to the spindle and shaft.
Yet another object of the invention is to provide a direct drive incorporating a servo motor capable of performing the load sensing methodology described and claimed in U.S. Pat. No. 5,454,777, eliminating the need for a load sensing circuit and a PLC.